The invention relates to a pivot bearing, in particular for a front wheel suspension system of a motorcycle. The invention furthermore relates to a front wheel suspension system for a motorcycle with such a pivot bearing.
A front wheel suspension system for BMW motorcycles, which has two trailing links arranged one above the other and in each case mounted pivotably on the frame or on the engine housing, is known under the designation “duo lever”. The front ends of the trailing links are in each case connected via a ball and socket joint to a fork like wheel carrier which—in contrast to the classic design with two sliding and fixed tubes in each case—is formed as a single part. The suspension and damping are undertaken by a suspension strut which is coupled to the lower of the two trailing links and is supported against the frame. The steering movements triggered by the rider are transmitted to the wheel carrier via a trapezoidal shear joint mounted on the steering head and wheel carrier.
It has already been recognized that ball and socket joints have to overcome a breakaway torque for the transition from static friction into sliding friction. In the case of the previously described “duo lever” front wheel suspension system, this relates to the movement of the wheel carrier and to the steering from a rest position.
As a solution to this problem, it is proposed in International patent document no. WO 2007/131590 A1 not to connect the front ends of the trailing links to the wheel carrier by spherical bearings but rather via pivot bearings in the form of rolling contact bearings, the pivot axes of which run transversely with respect to the longitudinal direction of the motorcycle. Said pivot bearings permit spring movements of the wheel carrier relative to the frame of the motorcycle. The further degree of pivoting freedom required for the steerability of the wheel carrier is achieved by a tube which extends between two transverse connecting elements (fork stabilizers) which connect the fork struts of the wheel carrier. The ends of the tube are each connected to the connecting elements via a pivot bearing. These two steering bearings are also formed by rolling contact bearings, and therefore breakaway torques are very substantially avoided even during the steering of the wheel carrier.
The combination of a plurality of standard rolling contact bearings for providing the required degrees of freedom for the suspension and the steerability of the wheel carrier according to International patent document no. WO 2007/131590 A1, however, requires a large amount of construction space. Further disadvantages are the high weight and the outlay on assembly.
It is an object of the invention to avoid these disadvantages and to permit a compact mounting which is simple to fit and has a plurality of degrees of freedom.
This object is achieved by a pivot bearing, which is provided in particular for a front wheel suspension system of a motorcycle, having a first bearing part which permits a component to pivot about a first pivot axis. The pivot bearing furthermore includes a second bearing part which permits a component to pivot about a second pivot axis, wherein the two pivot axes intersect. The two bearing parts are connected to each other and form a structural unit.
The invention is based on the finding that a combined pivot bearing with intersected pivot axes permits all movements which are required in the suspension and in the steering of the wheel carrier.
Owing to the combining of the two bearing parts to form a structural unit, the pivot bearing according to the invention is easier to handle and also affords logistical advantages in respect of storage and transport.
The pivot bearing according to the invention is suitable in particular for the front wheel suspension system of a motorcycle, particularly for the mounting of the wheel carrier. However, other use possibilities in which pivoting movements having a plurality of degrees of freedom are required are also possible.
According to the preferred embodiment of the invention, the first bearing part and/or the second bearing part have/has at least one rolling contact bearing, in particular a tapered roller bearing. With this bearing arrangement, the substantial problems associated with a ball and socket joint are overcome. In this connection, the breakaway torque which is virtually no longer present (considerably reduced static and also sliding friction) and the significantly lower temperature sensitivity (specifically in the vicinity of the engine) no longer stand in the way of use in chassis and steering system.
A configuration in which two tapered roller bearings which are inclined in relation to each other are fitted in the first bearing part and/or in the second bearing part, in particular in an O arrangement, has proved to be particularly advantageous. This configuration makes it possible to absorb radial and axial loads acting simultaneously (“combined loads”).
In the preferred configuration of the pivot bearing according to the invention, the first bearing part has a bearing housing in which a pin is rotatably mounted, and the second bearing part has an outer bearing shell in which a clamping bushing is rotatably mounted, wherein the bearing shell is formed in the pin or by the pin itself. The bearing housing is mounted fixedly in the installed state of the pivot bearing. The particular configuration with the pin which is rotatable in the bearing housing and the clamping bushing which is in turn rotatable in the pin permits a light and compact design of the pivot bearing with few components and which also requires little construction space.
So that the component to be coupled to the pivot bearing according to the invention can be mounted as easily as possible in the clamping bushing, the clamping bushing is preferably arranged in a portion of the pin that protrudes out of the bearing housing, and is therefore easily accessible.
According to an advantageous aspect of the invention, a preferably cylindrical portion of the pin, which portion faces away from the clamping bushing, is hollow, and a free edge of said portion is flanged outward. The hollow design of the pin portion saves weight and facilitates the flanging of the free edge. The flanging itself is advantageously used for fastening an adjacent bearing component, in particular a bearing ring, to the pin. In this case, it is possible to dispense with nuts or screws which cause weight, construction space and costs and have to be secured against release. The flanging therefore permits a saving on weight, cost and construction space and, in addition, increases the functional reliability of the pivot bearing according to the invention.
As already mentioned, a bearing ring which surrounds that portion of the pin which faces away from the clamping bushing can be supported on the flanged edge of the pin, wherein the outside diameter of the bearing ring preferably increases in the direction of the flanged edge. Owing to the flanging, the bearing ring is held securely on the pin.
The bearing ring constitutes a preferably slightly beveled rolling surface for first rolling contact bodies of the first bearing part, which rolling contact bodies are arranged between the bearing housing, on the one hand, and the bearing ring, on the other hand.
An arrangement, which is matched thereto, of a further tapered roller bearing is achieved by a configuration in which the pin has an intermediate portion which faces the clamping bushing and the outside diameter of which preferably increases in the direction of the clamping bushing, wherein first rolling contact bodies of the first bearing part are arranged between said intermediate portion and the bearing housing.
In a particularly compact configuration of the pivot bearing according to the invention, the pin has a cavity into which the clamping bushing is fitted, wherein second rolling contact bodies of the second bearing part are arranged between a wall of the cavity and the clamping bushing.
For an obliquely inclined second tapered roller bearing, the second rolling contact bodies rest on at least one ring surface of the cavity wall, the center axis of which runs parallel to the second pivot axis, wherein the ring surface or the ring surfaces is or are inclined relative to the second pivot axis.
In the preferred embodiment of the pivot bearing, the second rolling contact bodies rest on at least one inner ring which is coupled to the clamping bushing for rotation therewith. The clamping bushing together with the inner ring forms the inner part of a rolling contact bearing, which inner part is rotatable relative to the outer bearing shell.
According to a particularly advantageous aspect of the invention, at least one free edge of the clamping bushing is flanged outward, and a respective inner ring is supported on the one or two flanged edges of the clamping bushing, the outside diameter of which inner ring preferably increasing in the direction of the associated free edge of the clamping bushing. The hollow clamping bushing makes it possible in a simple manner to accommodate a component to be mounted, wherein the flanging can advantageously be used for fastening at least one inner ring to the clamping bushing. Owing to the flanging, the inner ring is held securely on the clamping bushing. In this case, it is possible to dispense with nuts or screws which cause weight, construction space and costs and have to be secured against release. The flanging therefore provides a saving on weight, cost and construction space and, in addition, increases the functional reliability of the pivot bearing according to the invention. The frustoconical shape of the inner ring is of importance for the configuration as an obliquely inclined tapered roller bearing.
In order to permit or at least to support a defined axial prestressing of the second rolling contact bodies, according to a development of the invention a spacer ring which surrounds the clamping bushing is arranged between the two inner rings.
The invention also provides a front wheel suspension system for a motorcycle, comprising a wheel carrier and trailing links or transverse links which connect the wheel carrier to a supporting component of the motorcycle, in particular to a motorcycle frame or an engine housing. The trailing links or transverse links are in each case connected by a pivot bearing of the type described previously to the wheel carrier.
Furthermore, the invention provides a front wheel suspension system for a motorcycle, comprising a wheel carrier in the form of a telescopic fork. At least one bearing point between a supporting component of the motorcycle, in particular a motorcycle frame or an engine housing, and the wheel carrier is formed by a pivot bearing of the type described previously.
With regard to the advantages of the front wheel suspension systems according to the invention, reference is made to the statements above regarding the advantages of the pivot bearing according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.